Every year in late April Earth passes through the dusty tail of Comet Thatcher (C/1861 G1), and the encounter causes a meteor shower--the Lyrids. This year the shower peaks on April 21st and 22nd. Unfortunately, bright moonlight will severely diminish the show.

The best time to look, no matter where you live, is during the hours before dawn on Tuesday, April 22nd. In years of little moonlight, observers typically count 5 to 20 meteors per hour. In 2008, however, most Lyrids will struggle to be seen in the moonlit sky. Only about 3 to 10 meteors per hour are expected.

Note: Rates could improve, in spite of the Moon, if the Lyrids undergo an outburst. This occasionally happens when Earth passes through a dense clump in the Lyrid debris stream (more on this below). The most recent outburst: April 1982 when 90 Lyrids per hour were observed.

Lyrid meteors appear to stream from the bright star Vega, more or less, as shown in the sky map below:

In fact, the Lyrids have nothing to do with Vega. The true source of the shower is Comet Thatcher. Every year in April, Earth plows through Thatcher's drawn-out dusty tail. Flakes of comet dust, most no bigger than grains of sand, strike Earth's atmosphere traveling 49 km/s (110,000 mph) and disintegrate as streaks of light--meteors!

Lyrid meteors are typically as bright as the stars in the Big Dipper, which is to say of middling brightness. But some are more intense, even brighter than Venus. These "Lyrid fireballs" cast shadows for a split second and leave behind smokey debris trails that linger for minutes.

Occasionally, the shower intensifies. Most years in April there are no more than 5 to 20 meteors per hour during the shower's peak. But sometimes, when Earth glides through an unusually dense clump of comet debris, the rate increases. Sky watchers in 1982, for instance, counted 90 Lyrids per hour. An even more impressive outburst was documented in 1803 by a journalist in Richmond, Virginia, who wrote:

"Shooting stars. This electrical [sic] phenomenon was observed on Wednesday morning last at Richmond and its vicinity, in a manner that alarmed many, and astonished every person that beheld it. From one until three in the morning, those starry meteors seemed to fall from every point in the heavens, in such numbers as to resemble a shower of sky rockets..." [ref]

What will the Lyrids do this year? The only way to know for sure is to go outside and look.

Experienced meteor watchers suggest the following viewing strategy: Dress warmly. Bring a reclining chair, or spread a thick blanket over a flat spot of ground. Lie down and look up somewhat toward the east. Meteors can appear in any part of the sky, although their trails will tend to point back toward the radiant--i.e., toward Vega.

Even if you see no Lyrids at all, you will definitely see Vega. Here are some fun facts about that star:

Vega is a brilliant blue-white star about three times wider than our Sun and 25 light years away. About 14,000 years ago Vega was the North Star. Earth's spin axis wanders: Now it points at Polaris, then it pointed at Vega. You might have seen Vega in Carl Sagan's movie Contact. It was the source of alien radio transmissions to Earth.